IDH2 and TET2 mutations synergize to modulate T Follicular Helper cell functional interaction with the AITL microenvironment

Angioimmunoblastic T cell lymphoma (AITL) is a peripheral T cell lymphoma that originates from T follicular helper (Tfh) cells and exhibits a prominent tumor microenvironment (TME). IDH2 and TET2 mutations co-occur frequently in AITL, but their contribution to tumorigenesis is poorly understood. We developed an AITL mouse model that is driven by Idh2 and Tet2 mutations. Malignant Tfh cells display aberrant transcriptomic and epigenetic programs that impair TCR signaling. Neoplastic Tfh cells bearing combined Idh2 and Tet2 mutations show altered cross-talk with germinal center B cells that promotes B cell clonal expansion while decreasing Fas-FasL interaction and reducing B cell apoptosis. The plasma cell count and angiogenesis are also increased in the Idh2-mutated tumors, implying a major relationship between Idh2 mutation and the characteristic AITL TME. Our mouse model recapitulates several features of human IDH2-mutated AITL and provides a rationale for exploring therapeutic targeting of Tfh-TME cross-talk for AITL patients.

Distinct and opposite effects of leukemogenic Idh and Tet2 mutations in hematopoietic stem and progenitor cells

Mutations in IDH1, IDH2, and TET2 are recurrently observed in myeloid neoplasms. IDH1 and IDH2 encode isocitrate dehydrogenase isoforms, which normally catalyze the conversion of isocitrate to α-ketoglutarate (α-KG). Oncogenic IDH1/2 mutations confer neomorphic activity, leading to the production of D-2-hydroxyglutarate (D-2-HG), a potent inhibitor of α-KG-dependent enzymes which include the TET methylcytosine dioxygenases. Given their mutual exclusivity in myeloid neoplasms, IDH1, IDH2, and TET2 mutations may converge on a common oncogenic mechanism. Contrary to this expectation, we observed that they have distinct, and even opposite, effects on hematopoietic stem and progenitor cells in genetically engineered mice. Epigenetic and single-cell transcriptomic analyses revealed that Idh2^R172K and Tet2 loss-of-function have divergent consequences on the expression and activity of key hematopoietic and leukemogenic regulators. Notably, chromatin accessibility and transcriptional deregulation in Idh2^R172K cells were partially disconnected from DNA methylation alterations. These results highlight unanticipated divergent effects of IDH1/2 and TET2 mutations, providing support for the optimization of genotype-specific therapies.

CD9 mediates the uptake of extracellular vesicles from cancer-associated fibroblasts that promote pancreatic cancer cell aggressiveness

In pancreatic ductal adenocarcinoma (PDAC), signaling from stromal cells is implicated in metastatic progression. Tumor-stroma cross-talk is often mediated through extracellular vesicles (EVs). We previously reported that EVs derived from cancer-associated stromal fibroblasts (CAFs) that are abundant in annexin A6 (ANXA6⁺ EVs) support tumor cell aggressiveness in PDAC. Here, we found that the cell surface glycoprotein and tetraspanin CD9 is a key component of CAF-derived ANXA6⁺ EVs for mediating this cross-talk. CD9 was abundant on the surface of ANXA6⁺ CAFs isolated from patient PDAC samples and from various mouse models of PDAC. CD9 colocalized with CAF markers in the tumor stroma, and CD9 abundance correlated with tumor stage. Blocking CD9 impaired the uptake of ANXA6⁺ EVs into cultured PDAC cells. Signaling pathway arrays and further analyses revealed that the uptake of CD9⁺ANXA6⁺ EVs induced mitogen-activated protein kinase (MAPK) pathway activity, cell migration, and epithelial-to-mesenchymal transition (EMT). Blocking either CD9 or p38 MAPK signaling impaired CD9⁺ANXA6⁺ EV-induced cell migration and EMT in PDAC cells. Analysis of bioinformatic datasets indicated that CD9 abundance was an independent marker of poor prognosis in patients with PDAC. Our findings suggest that CD9-mediated stromal cell signaling promotes PDAC progression.

Ketogenic HMG-CoA lyase and its product β-hydroxybutyrate promote pancreatic cancer progression

Pancreatic ductal adenocarcinoma (PDA) tumor cells are deprived of oxygen and nutrients and therefore must adapt their metabolism to ensure proliferation. In some physiological states, cells rely on ketone bodies to satisfy their metabolic needs, especially during nutrient stress. Here, we show that PDA cells can activate ketone body metabolism and that β-hydroxybutyrate (βOHB) is an alternative cell-intrinsic or systemic fuel that can promote PDA growth and progression. PDA cells activate enzymes required for ketogenesis, utilizing various nutrients as carbon sources for ketone body formation. By assessing metabolic gene expression from spontaneously arising PDA tumors in mice, we find HMG-CoA lyase (HMGCL), involved in ketogenesis, to be among the most deregulated metabolic enzymes in PDA compared to normal pancreas. In vitro depletion of HMGCL impedes migration, tumor cell invasiveness, and anchorage-independent tumor sphere compaction. Moreover, disrupting HMGCL drastically decreases PDA tumor growth in vivo, while βOHB stimulates metastatic dissemination to the liver. These findings suggest that βOHB increases PDA aggressiveness and identify HMGCL and ketogenesis as metabolic targets for limiting PDA progression.

Illuminating the cross-talk between tumor metabolism and immunity in IDH-mutated cancers

Mutations in the genes encoding isocitrate dehydrogenase 1 (IDH1) and 2 (IDH2) are key drivers of diverse cancers, including gliomas and hematological malignancies. IDH mutations cause neomorphic enzymatic activity that results in the production of the oncometabolite 2-hydroxyglutarate (2-HG). In addition to 2-HG's well-known effects on tumor cells themselves, it has become increasingly clear that 2-HG directly influences the tumor microenvironment (TME). In particular, the non-cell-autonomous impact of 2-HG on the immune system likely plays a major role in shaping disease development and response to therapy. It is therefore critical to understand how IDH mutations affect the metabolism, epigenetics, and functions of tumor-infiltrating immune cells. Such knowledge may point towards new therapeutic approaches to treat IDH-mutant cancers.

Abstract B170: Therapeutic implications of altered epigenetics and DNA damage responses in IDH2-mutated hematologic diseases

Acute myeloid leukemia (AML) and angioimmunoblastic T-cell lymphoma (AITL), are hematologic diseases requiring novel approaches to patient selection and therapy. In AITL, neoplastic cells express many markers of T follicular helper (TFH) cells, while in AML, myeloid stem and progenitor cells are affected. Tumor cells of AML and AITL patients frequently bear mutations affecting genes involved in epigenetic regulation, including isocitrate dehydrogenase (IDH) and ten-eleven translocation-2 (TET2). IDH mutations drive production of the rare metabolite D-2-hydroxyglutarate (2HG), which competitively inhibits α-ketoglutarate (α-KG)-dependent dioxygenases such as the TET proteins (affecting DNA methylation) and Jumonji histone demethylases (altering histone methylation). IDH mutations occur in 30% of AML and AITL cases but the spectrum of these mutations differs. In AML, IDH1R132 (41%), IDH2R140 (44%) and IDH2R172 (15%) dominate, and IDH and TET2 mutations are mutually exclusive. In AITL, IDH2R140 (2%) and IDH2R172 (98%) dominate (no IDH1 mutations), with co-mutation of TET2 in 82.1% of cases. In AML, loss of these dioxygenase activities causes epigenetic alterations to DNA and histones, leads to abnormal gene transcription that affects hematopoietic cell differentiation, and drives myeloid disease. However, in AITL disease, the impact of the IDH2 mutation is completely unknown. My goal is to dissect the effects of IDH2 and TET2 mutations in hematologic diseases to understand how IDH2 and TET2 mutations collaborate to drive malignancy in AITL, and why they cooperate differently in myeloid and lymphoid diseases. I focus on DDR signaling and epigenetics analysis to found novel therapeutic vulnerabilities arise from the altered epigenetic regulation and DDR linked to IDH2 and TET2 mutations. I used a CD4-Cre mouse model to introduce the IDH2R172K and TET2 mutations in the T-cell compartment. This would allow me to study the collaboration between IDH2 and TET2 mutations in the context of T-cells. Mice bearing both IDH2 and TET2 mutations show decreased survival, with a median survival of approximately 8 months accompanied by splenomegaly and lymphadenopathy. This is significantly different than CD4+ control mice or single mutant mice. Double mutant mice (DM) present a disruption of spleen and lymph node architecture. To understand this phenotype, I performed comprehensive flow cytometry staining and, surprisingly, I found that the increased spleen size is not due to T-cell infiltration, but is due to increased erythropoiesis and expansion of immature erythropoietic cells (CD71+, cKit+). We can explain this result by the fact that CD4-Cre is also expressed in some progenitor cells leading to stress induced erythropoiesis. However, if we focus on the T-cell population, we see that DM mice present a T-cell phenotype including a decrease of CD4+ naïve cells and an increase of CD4+ effector memory cells as early as 5 months. So, there is an imbalance in T-cell homeostasis, but only when both the IDH2 and TET2 mutations are present, suggesting a cooperative role for both mutations in T-cell development. Since both IDH2 and TET2 affect epigenetic regulation, I want to conduct experiments to understand how these changes modulate T-cells homeostasis. Moreover, emerging data support the hypothesis that connections exist between epigenetic regulators and DDR signaling in hematologic diseases. My final aim will be to attempt to evaluate the efficacy of treatment with IDH2 inhibitors, hypomethylating agents, or DDR-targeting drugs, alone or in combination in AITL disease and identify factors involved in responses to these therapies or in the development of resistance. Finally, I will compare results obtained in AML versus AITL mouse models and clinical samples to identify mechanisms that are shared, and those that are unique to each disease.

Citation Format: Julie Leca. Therapeutic implications of altered epigenetics and DNA damage responses in IDH2-mutated hematologic diseases [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr B170.

LIF Drives Neural Remodeling in Pancreatic Cancer and Offers a New Candidate Biomarker

Pancreatic ductal adenocarcinoma (PDAC) is characterized by extensive stroma and pathogenic modifications to the peripheral nervous system that elevate metastatic capacity. In this study, we show that the IL6-related stem cell-promoting factor LIF supports PDAC-associated neural remodeling (PANR). LIF was overexpressed in tumor tissue compared with healthy pancreas, but its receptors LIFR and gp130 were expressed only in intratumoral nerves. Cancer cells and stromal cells in PDAC tissues both expressed LIF, but only stromal cells could secrete it. Biological investigations showed that LIF promoted the differentiation of glial nerve sheath Schwann cells and induced their migration by activating JAK/STAT3/AKT signaling. LIF also induced neuronal plasticity in dorsal root ganglia neurons by increasing the number of neurites and the soma area. Notably, injection of LIF-blocking antibody into PDAC-bearing mice reduced intratumoral nerve density, supporting a critical role for LIF function in PANR. In serum from human PDAC patients and mouse models of PDAC, we found that LIF titers positively correlated with intratumoral nerve density. Taken together, our findings suggest LIF as a candidate serum biomarker and diagnostic tool and a possible therapeutic target for limiting the impact of PANR in PDAC pathophysiology and metastatic progression.Significance: This study suggests a target to limit neural remodeling in pancreatic cancer, which contributes to poorer quality of life and heightened metastatic progression in patients. Cancer Res; 78(4); 909-21. ©2017 AACR.

Abstract A61: CAF-derived ANXA6+-exosomes support pancreatic cancer aggressiveness and serve as a circulating biomarker

Pancreatic ductal adenocarcinoma (PDA) is one of deadliest human malignancies with a median survival barely reaching 6 months post-diagnosis. Such epidemiologic data highlight the urgent need to refine current therapies by integrating recent available knowledge on PDA biology. The malignant progression of PDA is characterized by the presence of an exuberant intra-tumoral microenvironment mainly composed of cancer associated fibroblasts (CAFs) and immune cells. This compartment interacts with pancreatic tumor cells surrounded by dense matrix and hypoxic areas, and affects their behavior through a poorly understood network. Indeed, cellular crosstalk between stromal and tumor cells is of major importance in pancreatic ductal adenocarcinoma (PDA). Here, by analyzing the proteomic stromal signature of human PDA, we highlight a possible contribution of the ANXA6/LRP1/TSP1 complex in such crosstalk. Following in vivo validations and stromal localization of each three candidates, we demonstrated that the formation of this complex is restricted to cancer associated fibroblasts (CAFs) cultured under physiopathological conditions (co-culture with macrophages, under hypoxia and lipid deprivation). Increased PDA aggressiveness is dependent on the uptake by tumor cells of CAFs-derived ANXA6+-exosomes. Targeting of ANXA6, and the relevant complex, in CAFs impairs PDA and metastasis occurrence while injection of ANXA6+-exosomes enhances tumorigenesis. Detection of ANXA6+-exosomes in serum is restricted to PDA patients and can distinguish PDA grade. Our data reveal a new CAF-tumor cell crosstalk supported by ANXA6+-exosomes and highlight a therapeutic target and an interesting biomarker for PDA.

Citation Format: Julie Leca, Sebastien Martinez, Sophie Lac, Jeremy Nigri, Veronique Secq, Marion Rubis, Nelson Dusetti, Celine Loncle, Julie Roques, Daniel Pietrasz, Stéphane Garcia, Samuel Granjeaud, Mehdi Ouaissi, Jean-Baptiste Bachet, Christine Brun, Juan L. Iovanna, Pascale Zimmermann, Sophie Vasseur, Richard Tomasini.{Authors}. CAF-derived ANXA6+-exosomes support pancreatic cancer aggressiveness and serve as a circulating biomarker. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Advances in Science and Clinical Care; 2016 May 12-15; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2016;76(24 Suppl):Abstract nr A61.

Cancer-associated fibroblast-derived annexin A6+ extracellular vesicles support pancreatic cancer aggressiveness

The intratumoral microenvironment, or stroma, is of major importance in the pathobiology of pancreatic ductal adenocarcinoma (PDA), and specific conditions in the stroma may promote increased cancer aggressiveness. We hypothesized that this heterogeneous and evolving compartment drastically influences tumor cell abilities, which in turn influences PDA aggressiveness through crosstalk that is mediated by extracellular vesicles (EVs). Here, we have analyzed the PDA proteomic stromal signature and identified a contribution of the annexin A6/LDL receptor-related protein 1/thrombospondin 1 (ANXA6/LRP1/TSP1) complex in tumor cell crosstalk. Formation of the ANXA6/LRP1/TSP1 complex was restricted to cancer-associated fibroblasts (CAFs) and required physiopathologic culture conditions that improved tumor cell survival and migration. Increased PDA aggressiveness was dependent on tumor cell-mediated uptake of CAF-derived ANXA6+ EVs carrying the ANXA6/LRP1/TSP1 complex. Depletion of ANXA6 in CAFs impaired complex formation and subsequently impaired PDA and metastasis occurrence, while injection of CAF-derived ANXA6+ EVs enhanced tumorigenesis. We found that the presence of ANXA6+ EVs in serum was restricted to PDA patients and represents a potential biomarker for PDA grade. These findings suggest that CAF-tumor cell crosstalk supported by ANXA6+ EVs is predictive of PDA aggressiveness, highlighting a therapeutic target and potential biomarker for PDA.

Abstract B06: Impact of intratumoral microenvironment and epithelial cells crosstalk in pancreatic carcinogenesis

Pancreatic adenocarcinoma (PDAC) is a cancer particularly resistant to current therapies. One possible reason consists in its cellular composition that limits access to drugs. Indeed, non-tumor cells, mainly activated fibroblasts (stellate cells) and immune cells, display 80% of the tumor mass composing the microenvironment or stroma. The stellate cells have the ability to secrete a lot of protein and extensive amounts of extracellular matrix which contributes to the formation of a fibrotic shield around epithelial cells, making those tumors highly hypoxic. Despite these knowledge the precise role of stromal components, and specifically stellate cells, in PDAC is poorly understood. In order to develop a simultaneous therapy targeting both tumoral and stromal cells, we investigate specific molecules implicated in the dialogue between those compartments to analyze their impact on pancreatic carcinogenesis.

In this study, we used a laser microdissection approach of human PDAC stromal and epithelial compartment, followed by mass spectrometry and bioinformatics analysis (statistics/interactome) to compare protein composition and networks within both compartments. We found the presence of a proteic complex composed of three proteins, expressed only in stromal compartment, related to lipid and intracellular trafficking. To validate such data, we confirmed the specific stromal expression of each protein, on human PDAC samples, and found that our three targets were expressed mainly in stellate cells. However before to investigate the dialogue between epithelial and stromal cells, we designed an in vitro model, based on co-culture of stromal cells: immune and stellate cells, which take into account the multi-cellular composition of such tumors and added PDAC relevant metabolic stresses: hypoxia and nutrient starvation. To improve our model, we used primary stellate cells that we extracted from freshly resected human PDAC tumor pieces. We added pancreatic tumoral cells in our model to investigate dialogue between stromal and tumoral cells. Our data show that under nutrient and hypoxic stresses, co-cultures from stellate and immune cells provide a proliferative and pro-migratory advantage to tumor cells. Moreover, and only in these same specific condition, the proteic complex identified is formed in stellate cells. So, we hypothesized that a specific “lipid related process” is developed by stellate cells in order to subvert the metabolically deprivated tumor cell.

To confirm such hypothesis, we designed shRNA against the three components of the complex to impair its formation and activity. Interestingly, we showed in vitro that, decreased expression of one protein can destabilize the complex in stellate cells and impair the proliferative and pro-migratory advantages to tumor cells. In parallel, in vivo, we designed an intra-pancreatic co-injection model of tumor and stromal cells in mice. Our experiments suggest that co-injection of stellate cells with tumoral cells increases tumorigenesis, an advantage which is lost if we co-inject stellate cells that carry a shRNA against anyone of the three targets. This is correlated with a decreased survival of tumoral cells within those tumors, stained for apoptotic and proliferative markers as wells as measured for their necrotic areas.

At present, in order to confirm this protein complex as a potential therapeutic target as adjuvant to Gemcitabine or Folfirinox, we need to deepen the mechanisms of communication between stellate and tumoral cells and more specifically its impact on exosome processes. Altogether, our data suggest that if we prevent aids setting up by stellate cell, through destabilization of this complex within stellate cells, it could sensitize tumor cells by decreasing their survival abilities and certainly enhances their response to chemotherapies (under investigation).

Citation Format: Julie Leca, Véronique Secq, Jérémy Nigri, Sébastien Martinez, Marion Rubis, Marie Noelle Lavaut, Nelson Dusetti, Céline Loncle, Stéphane Garcia, Philippe Chan, Magalie Benard, Juan Lucio Iovanna, Christine Brun, Sophie Vasseur, Richard Tomasini. Impact of intratumoral microenvironment and epithelial cells crosstalk in pancreatic carcinogenesis. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Innovations in Research and Treatment; May 18-21, 2014; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2015;75(13 Suppl):Abstract nr B06.

Stromal SLIT2 impacts on pancreatic cancer-associated neural remodeling

Pancreatic ductal adenocarcinoma (PDA) is a critical health issue in the field of cancer, with few therapeutic options. Evidence supports an implication of the intratumoral microenvironment (stroma) on PDA progression. However, its contribution to the role of neuroplastic changes within the pathophysiology and clinical course of PDA, through tumor recurrence and neuropathic pain, remains unknown, neglecting a putative, therapeutic window. Here, we report that the intratumoral microenvironment is a mediator of PDA-associated neural remodeling (PANR), and we highlight factors such as 'SLIT2' (an axon guidance molecule), which is expressed by cancer-associated fibroblasts (CAFs), that impact on neuroplastic changes in human PDA. We showed that 'CAF-secreted SLIT2' increases neurite outgrowth from dorsal root ganglia neurons as well as from Schwann cell migration/proliferation by modulating N-cadherin/β-catenin signaling. Importantly, SLIT2/ROBO signaling inhibition disrupts this stromal/neural connection. Finally, we revealed that SLIT2 expression and CAFs are correlated with neural remodeling within human and mouse PDA. All together, our data demonstrate the implication of CAFs, through the secretion of axon guidance molecule, in PANR. Furthermore, it provides rationale to investigate the disruption of the stromal/neural compartment connection with SLIT2/ROBO inhibitors for the treatment of pancreatic cancer recurrence and pain.